2011 MTM Audi S5 Cabriolet

Hit by a bus: MTM hacks into the S5's CAN-bus port and turns up the power.

With the last ergs of performance and efficiency already wrung out of today’s production engines, you’d have thought even the best independent tuning houses would have packed up their engine dynos and gone home. Instead, these conditions have bred a superstrain of tuner, resistant to the power war’s asymptotic virus. These shops—Dinan, Hennessey, and Alpina, for three—are able to keep squeezing out more juice without losing much of a car’s overall integrity. German tuner MTM aims for a place alongside them.

Former Audi engineer Roland Mayer founded MTM (Motoren Technik Mayer) in 1990; the turbocharged inline-five sits atop his résumé. Currently, Mayer’s firm tunes most of the VW Group brands, as well as Spyker, Ferrari, KTM, and Porsche cars. His newest product is the Cantronic system, a CAN (Controller Area Network)-bus-modification unit that bores into the vehicle’s brain and makes it do funny things.

Who You Calling Funny?

In the case of this MTM S5 3.0T cabrio, Cantronic infects the engine with an additional 97 hp (for a peak of 430) and 55 more lb-ft of torque (up to 380) by modifying boost pressure and fuel delivery. Unlike back-alley chip tuning, Cantronic maintains adaptive control of these parameters to balance power, efficiency, and engine life, and the unit can be removed easily. These guys are getting smarter.

With smarts come savings. The Stage 3 Cantronic on our test car costs barely more than $3000. (Stage 2 nets you 380 hp for $2500, and Stage 1 loosens the governor, allowing for a 171-mph top speed, for about a grand.) However, the package we drove came wearing about $15,000 worth of accessories in addition to the ECU lobotomy (all parts are available separately, either through Hoppen Motorsport of Sarasota, Florida, or MTM.) Our S5 wore 15-inch front brake discs pinched by four-piston calipers, 20-inch forged aluminum wheels wrapped in 265/30 Michelin Pilot Sport 2s, one-inch-shorter springs, and a 2.8-inch stainless-steel exhaust responsible for exactly zero of the extra hp. Which begs the question “Why?” until you hear it yelp.

Our test car was 39 pounds porkier than the softtop S5 3.0T we weighed last fall, but with better mass distribution (53.2/46.8 percent front to rear versus 54.5/45.5). It’s a significant 637 pounds lumpier than the nose-heavy S5 V-8 coupe we last put on the scales in 2008 (S5 coupes retain their 354-hp, 4.2-liter V-8s for 2011; all S5 cabrios come with blown sixes). When Audi swapped out the S4’s and S5 cab’s eights for sixes, it argued that the downsized engine’s lower weight and equivalent 325 lb-ft of torque would make 0-to-60 sprints a wash. MTM not only surpasses the cabrio’s acceleration but also brings the car into line with the lighter S5 coupe, managing the run in 4.7 seconds versus 4.8 in the big-engined car (the stock 3.0T cab hits 60 in 5.1 seconds). In the quarter-mile, the MTM cabrio matches the coupe’s elapsed time of 13.4 seconds but betters its trap speed by 2 mph: 107 to 105. Skidpad grip, at 0.91 g, fails to build on the stock cabrio’s excellent performance.

Mood: Enhanced

MTM’s mods change the character of the S5 more than these numbers might suggest. Whereas all varieties of Audi S5 come across as seamless and deliberate, the MTM is entirely flint and bark. It rides roughly over potato-chipped roads, and its brakes can be shrill. It makes up for this with astounding body control, tree-frog grip, a tendency to shoot out of corners like somebody called its momma a bad name, and the ability to release all its power in a great wave.

One thing about that power delivery, though: The Cantronic system shifts the torque peak from 2900 rpm in the stock engine to 4760. As a result, there’s some lugging at low revs in the normal transmission mode as the seven-speed DSG hunts for torque. Alas, Cantronic doesn’t change transmission programming. You’re much better off using the paddles behind the wheel or keeping the trans in sport mode. That way, you’ll keep the 3.0T humming. This engine is a puller, and MTM’s modified version rushes toward redline with even greater determination.

But is this car superior to the series S5? It’s certainly far more expensive: Our tester tickled $85,000—about $25,000 more than a base S5 cab—proof that nobody knows how to charge for horsepower like the Germans. There are a lot of cars we could have for that kind of money, and most of them start with a P, possibly an N. This particular car was not as fully realized as the base S5, or even the best from Alpina, et al. But $3000 for the intelligent, removable Cantronic system? That is totally worth it.

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*AccuPayment estimates payments under various scenarios for budgeting and informational purposes only. AccuPayment does not state credit or lease terms that are available from a creditor or lessor, and AccuPayment is not an offer or promotion of a credit or lease transaction.